• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.9-15
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• 2018

The turbochargers, which are used widely in diesel and gasoline engines, are an effective device to reduce fuel consumption and emissions. On the other hand, turbo-lag is one of the main problems of a turbocharger. Bearing friction losses is a major cause of turbo lag and is particularly intense in the lower speed range of the engine. Current turbochargers are mostly equipped with floating bearings: two journal bearings and one thrust bearing. This study focused on the bearing friction at the lower speed range and the experimental equipment was established with a drive-motor, load-cell, magnetic coupling, and oil control system. Finally, the friction losses of turbochargers were measured considering the influence of the rotating speed from 30,000rpm to 90,000rpm, oil temperature from $50^{\circ}C$ to $100^{\circ}C$, and oil supply pressure of 3bar and 4bar. The friction power losses were increased exponentially to 1.6 when the turbocharger speed was increased. Friction torques decreased with increasing oil temperature and increased with increasing oil pressure. Therefore, the oil temperature and pressure must be maintained at appropriate levels.

• Water for future
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• v.28 no.5
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• pp.141-150
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• 1995

An air chamber is designed to keep the pressure from exceeding a predetermined value, or to prevent low pressures and column separation. Therefore, it can be used to protect against rapid transients in a pipe system following abrupt pump stoppage. In this research, an air chamber was applied to a hypothetical pipe system to analyze attenuation effect of pressure head for different air volumes, locations, chamber areas, coefficients of orifice loss and polytropic exponents. With an increase of air volume, the maximum pressure head at pump site is decreased and the minimum pressure head is increased. For different locations and areas of the chamber, the attenuation effects do not show much difference. Also, as the orifice loss coefficient increases, the maximum pressure head is decreased. For different polytropic exponents, isothermal process shows lower maximum pressure head than that of the adiabatic process.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.194.1-194
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• 2001

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1995.10a
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• pp.59-61
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• 1995

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.137-137
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• 1999

• Plant Journal
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• v.9 no.1
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• pp.6-11
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• 2013

• Proceedings of the Membrane Society of Korea Conference
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• 2000.04a
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• pp.43-46
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• 2000

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.614-618
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• 2014

본 연구에서는 디퓨저의 압력회복을 높이기 위해 디퓨저 입구에 실린더를 설치하여 후류가 압력회복에 어떤 영향을 미치는지 알아보았다. 2D-Incomp-2.1-P 해석자를 이용하여 속도, 압력에 따른 유동가시화를 통해 내부유동을 분석하였고, 압력회복계수를 비교하여 디퓨저 입구에 설치된 실린더의 후류가 디퓨저 성능에 어떤 영향을 주는지 비교하였다. 그결과 실린더를 설치하였을 때 확대부에서의 박리영역이 더 작아졌고 압력회복계수가 더 높아졌다.

• Journal of Power System Engineering
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• v.14 no.3
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• pp.25-32
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• 2010

전 세계적으로 급속도로 인기가 더해가고 있는 수소에너지는 높은 전환 효율성, 재생성, 친환경적인 특징을 가지며 미래의 주 에너지가 될 것이다. 왕복동식 압축기를 통과한 후의 수소 가스의 압력은 높은 맥동압을 가진다. 스너버는 압축기의 한 구성품으로 맥동압을 낮추고 수소가스의 불순물을 제거하기 위해 사용된다. 이 연구에서의 실험은 스너버 시스템에 사용된 강관의 맥동에 관해 조사하기 위해서 수행되었다. 맥동압은 12 Hz ~ 60 Hz의 모터속도에서 RMS값을 기준으로 0.1625% ~ 0.5305% 그리고 평균압력을 기준으로 0.1621% ~ 0.5277% 감소하였다. 압력손실은 RMS값을 기준으로 0.1092% ~ 1.4419%, 평균압력을 기준으로 0.1493% ~ 1.7507%로 측정되었다. CFD를 이용한 수치해석값은 실험값이 거의 비슷한 결과를 나타내고 강관 관로 내부 가스의 자세한 압력을 설명하기 위한 중요한 역할을 수행한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.732-739
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• 2016

In Korea, the summer is hot and humid, and much electricity is consumed for air conditioning. Thus, the simultaneous usage of an indirect evaporative cooler and a common air conditioner could reduce the sensible heat and save electricity. This study developed a U-type cross-counter flow indirect evaporative cooler (IEC) made of plastic and paper. The efficiencies were compared with those of a cross-flow IEC. The specimen was $500mm{\times}500mm{\times}1000mm$. the results show that the indirect evaporation efficiencies of the cross-counter flow sample were 6-21% higher than those of the cross-flow sample. The pressure drops of the cross-counter sample were 51-66% higher. Thermal analysis based on the -NTU method predicted the experimental data within 10%. The electrical energy saved by the use of the cross-counter flow IEC was larger than that of the counter flow IEC, and the difference increases with the velocity. However, the the cross-counter IEC is two times larger than the cross-flow IEC, which may increase the material cost and water usage.